How you cite a GIF depends on where it appears. If the GIF is part of a larger work, cite the work and refer to the GIF in your prose. As always, key your in-text citation to the first element of the works-cited-list entry:

In a BuzzFeed post on aging, a pair of GIFs demonstrates how much easier it is to lose weight in one’s early twenties than in one’s late twenties (Misener).